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Sour-To-Acid concept for sour gas fields

Summary

The production of large quantities of solid sulphur makes sour gas field development costly and challenging. In this article, M. Gierman, P. Micone, M. Lebel and V. Léveillé of Shell Cansolv introduce the application of Sour-To-Acid as a development concept for sour gas fields. The Sour-To-Acid concept, enabled by Cansolv SO2 Scrubbing technology, converts sulphur containing molecules directly into sulphuric acid, which makes it especially attractive where sour gas fields can be linked with a large sulphuric acid demand e.g. in the Middle East, Russia and Brazil.

Abstract

Recent years have demonstrated that for an increasing number of countries it may be difficult to meet their future local gas demand and gas export commitments1. Especially in the Middle East, domestic power demand is increasing due to a growth in population, higher living standards and development of new energy intensive industries (petrochemical, metal smelters, etc.). Additionally, gas injection is applied more frequently to boost the life time of oil producing fields. In order to fulfil future gas demands, resource owners are forced to develop more complex gas fields like sour gas fields which were previously regarded as economically unattractive.
The development of a sour gas field has many challenges, not only health, safety and environmental (HSE) aspects, which need to be reflected in the design of the surface facilities, but also challenges related to the continuous drive to minimise the environmental footprint from the surface facilities. This results in stringent SO2 emission targets and corresponding ultra high sulphur recovery efficiency (SRE) requirements. In order to meet these requirements, sophisticated technologies need to be applied to develop sour gas fields2. These challenges are combined with high availability targets, large uncertainties in feed gas compositions, fluctuating rates and limited availability of skilled labour for construction.
Keywords: sour gas field development, sulphuric acid, S2A concept, acid gas removal, Cansolv SO2 scrubbing

Sour water stripping – Part 1: Non-phenolic water

Summary

Most non-phenolic sour water strippers for removing ammonia and hydrogen sulphide from refinery sour water are built with 30 to 60 trays and are usually designed using equilibrium stages and stage efficiencies. However, overall tray efficiency values are quoted over the rather wide range from 15% to 45%, corresponding to a three-fold range in the potential tray count. Recently a mass transfer rate-based simulator has become available for designing and troubleshooting SWSs. This article focuses on the proper description of phase equilibrium in uncontaminated sour water and the use of a mass transfer rate-based model to develop better information on efficiency factors.

Abstract

Dealing with sour water is a reality that most refiners must face. Most refinery sour water sources contain relatively little carbon dioxide; it is the hydrogen sulphide content that makes water “sour”. When present together, ammonia and hydrogen sulphide have almost unlimited solubility in water.
Gaseous ammonia will continue to be absorbed as long as it becomes protonated as a result of H2S co-absorption. Thus, it is conceivable that a particular sour water stream may be a lot more concentrated in both ammonia and hydrogen sulphide than the solubility of either component alone would suggest is even remotely possible.
Keywords: mass transfer rate, modelling, weir height, tray efficiencies, ammonia removal, stripper pressure

Hydrogen and sulphur from hydrogen sulphide

Summary

Superadiabatic autothermal reforming, or SuperATR, is being developed as a new and novel method to extract hydrogen and sulphur from hydrogen sulphide. A first generation SuperATR bench-scale reformer obtained a 31% hydrogen yield. Improvements to the first generation reformer resulted in a 38% single pass hydrogen yield in addition to 70% sulphur. With recycling of the unreacted H2S, a commercial process based on the second generation SuperATR process is expected to yield up to 50% hydrogen and 99.9% sulphur.

Abstract

Hydrogen is being touted as a miracle fuel due to its near zero emissions properties when burned. It produces no greenhouse pollutants and almost no pollutants causing acid rain when combusted. Currently, most hydrogen is obtained from the reforming of natural gas or partial oxidation of coal. Only a minute amount of hydrogen is produced via electrolysis of water, a renewable but expensive energy option.
Most methods that generate hydrogen from natural gas are also fairly expensive and generate greenhouse gas. Hydrogen sulphide, on the other hand, is a toxic waste generated in oil refining and natural gas processing plants. Hence, a process that can extract the hydrogen content of H2S would be superior to generating hydrogen from natural gas, because it would at the very least be carbon-free and most likely inexpensive.
Keywords: superadiabatic autothermal reforming, SuperATR, Innovative Energy Solutions, thermal cracking

SWS design and operation

Summary

Jacobs Comprimo Sulfur Solutions describes various sour water stripping designs that can be applied depending upon different client specifications and WorleyParsons discusses SWS operations and some of the pitfalls that can be experienced when sour water stripping systems are not properly designed and operated. A case history about tray fouling and various lessons learned from different operating sites is presented.

Abstract

Sour water stripping (SWS) is one of the first stages in the waste water treatment process in many industrial operations, and especially in refineries. Water streams from throughout a refinery are typically sent to the stripper to remove both H2S and ammonia from the water. In some cases the ammonia and H2S are separated and sent to individual destinations, but in the majority of SWS set-ups the effluent acid gas from a sour water stripper overhead is processed in the sulphur plant (SRU). There are several designs of sour water strippers, for example, the standard design that Jacobs Comprimo Sulfur Solutions offers for its sour water strippers comprises the following steps:
l flashing of the sour water stream at close to ambient conditions, to remove as much hydrocarbons as possible;
l overhead condenser with gas temperature of 85-90°C, to prevent ammonium salt formation and minimise water vapour content (lower water content is beneficial for the downstream sulphur recovery unit);
l reboiler (vertical thermosyphon or ‘plate and frame’ type) operated at a bottom pressure of 1-1.3 barg, to minimise reboiler steam consumption and enable an overhead gas pressure high enough to process gas in the downstream sulphur recovery unit. LP steam consumption is in the range of 150-190 kg steam per m3 sour water. Direct steam injection can be used as a backup.
Keywords: sour water stripping, pumparound systems, tray fouling, caustic injection, troubleshooting

Debottlenecking for capacity increase

Summary

A number of strategies can be employed to increase the capacity of existing metallurgical and sulphur-burning sulphuric acid plants, including increasing the SO2 gas strength and lowering the pressure drop of the plant. An efficient way to increase plant capacity without increasing the SO2 emission is to tailor a catalyst solution that provides more activity in the existing converter.

Abstract

Noram upgrade concepts
Acid plants frequently require capacity increase. Several factors are important to identify a practical limit for capacity increase. NORAM has experience engineering solutions that increase acid production by 30% and steam production by 40%, while reducing the stack SO2 concentration by 15%. These are some of the strategies that are proven to be effective:
SO2 gas strength
In general, increasing the concentration of SO2 in the process gas is the most cost-effective way to increase sulphuric acid plant capacity. This change may allow for increased production, without significant changes to the plant pressure profile, equipment hydraulic performance and main blower capacity. This is particularly important when the main blower is already operating at its maximum capacity.
Keywords: SO2 gas strength, pressure drop, gas heat exchangers, tower packing, low pressure drop catalyst, heat recovery, HEROS

The global sulphuric acid market – a look back and to the future

Summary

Fiona Boyd and Freda Gordon of Argus Media take a historic look at the global sulphuric acid market, as well as a look forward to what can be expected from the "king of chemicals".

Abstract

Since the 1990s, global production of sulphuric acid has increased significantly. Along with greater availability, the boom in many commodity prices in 2007-08 saw new market players emerge. Despite a year of survival in 2009 following the global economic recession, many of the newer companies remained involved in the traded sulphuric acid market. The emerging trend now, however, is one of consolidation in the industry despite the forecast for even greater production.
1990s – low prices in downstream markets
In the mid-1990s, world sulphuric acid trade volumes were around 6.5 million t/a, accounting for mostly short-haul trade within Europe, Asia and North America. These regions were key suppliers because of their base metal smelters, the primary source for traded sulphuric acid, and that regional dominance remains today. At that time, prices in the global sulphuric acid and related markets were low compared with today’s levels. The US Gulf/Tampa import price for sulphuric acid was the benchmark price, and it was around $30/t c.fr. Meanwhile, the molten sulphur benchmark price was $60/long ton delivered at Tampa, while the solid sulphur export price was around $60/t f.o.b. ex-Vancouver. In the fertilizer market, then and still the primary consuming market of sulphur and sulphuric acid, the diammonium phosphate (DAP) price was $175/t f.o.b. Tampa for exports, while the copper price, then not seen as a significant indictor for the markets, was around $0.85/lb.
Keywords: SMELTING, LEACHING, INTERACID, SUMITOMO, TAMPA, COPPER, METALS, CHILE, PHILIPPINES